The decision came on the heels of the Tribe's recent 11-game losing streak, which sent the club stumbling out of the discussion for the American League Central crown. The skid was the second-longest losing streak in the 112-year history of the franchise, and the biggest issue throughout the slump was the team's starting pitching.
Starters went a combined 0-8 with a 10.44 ERA over the 11-game losing streak, which ended with a 6-2 win over the Twins on Wednesday afternoon. During the drought, Antonetti and manager Manny Acta discussed making a change at the pitching coach position, but they did not finalize things until Thursday.
That is when Radinsky received the news.
"We talked to Scott today," Antonetti said. "Certainly, we were mindful as we were going through the losing streak of how we were pitching at that point, but at the same time we didn't feel it was appropriate to make that decision while we were in the midst of it.
"We didn't think that Scott should bear the burden of the losing streak. We made the decision, and then informed him today."
It came as a shock to Cleveland's pitchers.
"I wasn't coming to the ballpark expecting to deal with that today," closer Chris Perez said. "The thing Antonetti said to us was it's one thing to be underperforming and not doing your job and not pitching well, but he didn't see any signs of us getting better. That was a big thing for him to let Rad go.
"He didn't see anybody making any kind of strides, which I can agree with. It's been one of those, especially this last stretch here, it's been bad. You can't really put a finger on it."
The rotation issues were magnified throughout the 11-game losing streak, but it has been an ongoing problem during this trying season for Cleveland.
Radinsky, who shifted from bullpen coach to pitching coach this season, oversaw a rotation that entered Thursday with the most losses (50) and walks (261), and the highest WHIP (1.51) among the AL starting staffs. Cleveland's 5.10 rotation ERA ranked 12th in the AL.
Overall in the AL, the Indians' pitching staff ranked 13th in ERA (4.75), earned runs (521) and strikeouts (728), and last in runs allowed (571), walks issued (395) and WHIP (1.43). Since May 24, when the Tribe was 26-18 and in first place, the rotation has gone 19-37 with a 6.01 ERA and a .296 opponents' batting average.
"We were expecting, especially our starting rotation, to be better," Acta said. "That's not all on Rad. He can't go out there and pitch for these guys, but certainly we expected some of the guys to take a step forward and it just didn't happen."
The rotation has seen a high amount of turnover as a result.
Last week, Derek Lowe (8-10, 5.52 ERA) was designated for assignment and Josh Tomlin (5-8, 5.82 ERA) was demoted to the bullpen. Jeanmar Gomez (4-7, 5.18) was sent back to Triple-A Columbus earlier this season. Zach McAllister, Corey Kluber and Chris Seddon each joined the Tribe from Triple-A at various points.
Through it all, the two pitchers expected to be the rotation anchors, Justin Masterson and Ubaldo Jimenez, have been incredibly inconsistent. Masterson, who turned in seven strong innings on Wednesday to help end the losing streak, is 8-10 with a 4.68 ERA, and Jimenez is 8-11 with a 5.29 ERA.
Radinsky, who has been in the Indians' organization since 2004, and took over for former pitching coach Tim Belcher this season, paid the unfortunate price.
"It's a sad, awful day," Acta said. "All the blame doesn't rest on his shoulders. All of us are to blame -- even his pitchers, themselves. That's how the game works. There's no doubt when we made the decision [to hire Radinsky] that he was prepared to be our pitching coach."
Niebla, 40, joins Cleveland as one of the highest regarded pitching coaches in the Minor Leagues. He has been in the organization for 12 seasons, beginning in 2001, and was named to the XM All-Star Futures Game coaching staff in each of the past two seasons.
Niebla worked as an assistant to the Indians' Major League coaching staff in 2010, but he has spent the bulk of his coaching career as a pitching coach at multiple levels in the Tribe's farm system. Last season, he helped Triple-A Columbus post its best team ERA (3.94) since 1994 and led a staff that set a Clippers single-season record for strikeouts (1,142).
Signed as a non-drafted free agent by the Expos in 1995, Niebla has six years of professional pitching experience. In stints with the Expos and Dodgers, as well as some time in independent baseball, Niebla went 29-27 with a 4.11 ERA in 195 professional appearances.
"[Niebla] has worked very closely with a lot of these guys already," Antonetti said, "and has been instrumental in some of their development. In a lot of cases, we've seen very tangible results from his coaching, how guys have gotten better under his tutelage. We're hopeful that he can transition some of that expertise and knowledge to the group of guys who are up here.
"He's got a very good feel for the game. He's got a very good feel for pitching, mechanics, how to attack hitters, the mental side or the game as well and he's got some great experience as a pitching coach."
Pitchers were upset to see Radinsky go, but they understood the change.
"The team felt like we still have a month-and-a-half to get somebody new in here," Perez said, "try to maybe shake things up and get us going again, try to find maybe a new voice on the outside looking in that can maybe see something different.
"We underperformed this year. It's as easy as that. It stops with the pitching staff. Coming into Spring Training, we knew we kind of had the same offense we had last year. We were going to have to rely on our pitching staff. Unfortunately, it hasn't worked out."